Measuring instrument



Nov. 10, 1942. c. l. BRADFORD 2,301,197

MEASURING INSTRUMENT Filed Sept. 26, 1941 2 Sheets-She et 1 4 I IMPULSEI-ZZS 40 I 1 ounce 7 'OOKC ScmJNG FREQUENLY 6 :25

Hi l E J b Q It Q Q I I DO PLATE vozJ-nas 0 1 4g. 7 INVENTOR 5 Cou/v levnva Elmore/ea 9 BY TIME AZORNEYS Nov. 10, 1942. c. BRADFORD MEASURING INSTRUMENT Filed Sept. 26, 1941 2 Sheets-Sheet 2 time measuring instruments.

urement of time intervals is needed in .many pre Patented Nov. 10, 1942 Colin Irving Bradford, Fair-field, Conn, assignor to Remington Arms Company, Inc.,.a corporation of Delaware Application September 26, 1941, Serial No. 412,473

15 Claims.

This invention relates to an apparatus for counting impulses and particularly impulses of a known frequency over an interval so as to measure the time of the interval. It will be described particularly in its use in an instrument for measuring time intervals, although it isto be distinctly understood that it is applicable to other than Accurate meascision devices, and as one example thereof, a device formeasurement of the time of flight of a projectile through the barrel of a gun may be cited. Accurate measurements of time intervals.

are also desired in other instruments such as depth sounding devices, instruments for meas-- -uring the operation of relays and, circuit breakers," and locat'ors, and many other operations involvingtime intervalsfrom which an electrical impulse can be obtained at the beginning and end of the interval.

for anypurpose wherein two impulses are. avail- The invention may also be used able, denoting the beginning or end of the interval, operation or process involved, andin which there are impulses to be counted during theinterval.

, One of the objects of this inventionis to protor "fora period of time after the operation has taken place. From the following illustrative description in which are disclosed certain embodiments'of the invention as well as means and details of carrying it out, it will become apparent.

how the foregoing and other bjects may be accomplis'hed.

; .Inthe drawings:

Flg. Iis a'fragmentary and schematic diagram showing one of the fundamental circuits of the present invention.

Fig.'f2 is a circuit diagram of one form of the Most of the methods of measuring short time intervals measure the time in terms of some other factor. As an example, the Boulenge chronograph measures time in terms of distance and the gravitational constant. This is done by means of th release and free drop of a rodya mark being placed thereon denoting the end of the interval. Other types of chronoscopes measure time in terms of an electrical charge, whereas, in the present invention, the time is measured in terms of time. The basis of operation of this invention is the counting of the number of cycles of a known frequency source elapsing vide an accurate instrument for measurement 1f otshort or long time intervals which is extreme- Ilyfaccurate and can be easily read by an operaconstant-frequency generator and its amplifier.

Fig, 3 is a c rcuit diagram of one-type of switching circuit which may be used.

Fig. 4 is acircuit diagram of an instrument having four counting scales, a monitoring device and various other features which will appear in the detailed description thereof.

Fig. 5 is a graphic representation of a counting operation.

Fig.6 is a schematic diagram of a use of the invention for counting irregular impulses.

F g. '7 is a graph showing the relation between plate voltage and plate current of a desirable tube.

the other measuring condensers.

during the unknown interval. When it is used to measure irregular impulses, it is evident that the interval maybe predetermined and that the instrument will then read the number of impulses received during said predetermined'interval. The

source of constant frequency may be held to within a few parts in a million by various well-- known means. An example. of such is a con- .ventional piezo-electrical crystal standard frequency apparatus.

If the frequency is chosen high enough, errors in practical measurements will be negligible. By choosing one hundred thousand cycles per second as a standard frequency, the interval can be measured to within 'Vmouoo Of a second.

In the present invention, means are provided to successively produce one impulse for a given number of impulses, andto record the number of impulses in each stage at the end of the inter val; for example, the source of constant frequency can be mployed to charge a first condenser a predetermined number of impulses, which will then break down and produce a single impulse. This single impulse may be impressed upon the next condenser, which can be designed to build up the same predetermined number of impulses and create an impulse which may be impressed On the next measuring condenser, this being rcpeated until the desired number of nu-.

merical places are obtained. It is, of course, to be understood thatthe first condenser immediately upon discharge will repeatedly charge and discharge during the interval, and similarly for Then, when the interval is completed, the charge on each condenseror the number of impulses on each condenser may be measured, which will give a time interval measurement.

Referring particularly to Fig. 1, there will be found the bare essentials of a fundamental circuit which may be employed, it being understood,

of course, that certain of'the usual condensers and resistances are omitted for purposes of illustration. At I there is indicated diagrammatically a source of constant, frequency, which in this case may be 100 kilocycles, although it is to be distinctly understood that the frequency used is a matter of choice and may be other than 109 kilocycles. The details of the source of constant frequency will be discussed at a later point. H represents diagrammatically a switching circuit having an input between terminals l2 and an input between terminals l3. An input may be used to receive an impulse at the beginning of the interval and one for an impulse at the end of the interval so as to energize the switching circuit during the interval. The output which is employed may be at terminal I4. A tube i5 having a control grid l6, cathode I1 and plate I8 is used.. It is to be understood that wherever the term cathode is used, it may be indirectly or directly heated, and that plate means the same as anode and control grid the same as "control element. .The plate voltage vs. plate current family of characteristics should be similar to that shown in Fig. '7, having substantially flat plate current vs. plate voltage curves. As is well known in the art, various types of tubes may be used to obtain such a characteristic, and as an example of such a tube, a pentode 1852 may be used, although it is distinctly understood that the invention is not limited thereto. The graph shown in Fig. 7 is specifically for an [852 pcntode and is that desirable for the scaling tube. Tube l5 may be called the scaling tube and tube 22 the discharge tube. The output 19 of the source of constant frequency is impressed on the grid 16. The grid, however, is biased so that the tube remains normally non-conducting, except during the time of the interval. It is evident that the tube will conduct during the recurrent pulses of the source which may or may not occur at the exact instant the bias of the tube is changed so that it becomes conductive or capable of conducting the impulses. The switching circuit at II will be described later, but in general it may be of the type shown in applications, S. N. 276,167 or-334,300, or any other suitable kind. In such a switching circuit, a flow of current occurs during the interval, and the potential developed as the result thereof may be impressed upon grid Hi. This will so bias the grid that during the positive half cycles of the source of constant frequency the tube will become conducting and an impulse will take place in the plate circuit thereof during each positive half cycle of the source of constant frequency. Inasmuch as this is during the interval, it will be evident that the number. of impulses passing through the plate circuit of tube l5 will give a direct indication of the time. Because there are so many of these impulses in a short space of time, it is necessary to provide some means of is discharged. This is accomplished in the present invention by placing condenser 20 in the plate-cathode circuit of the electronic tube 22. This tube may be of the gaseous type or a high vacuum tube having triggering characteristics, and the term electronic control tube is to be understood to so mean. This circuit will then be from condenser 20, line 23, winding 24, plate 25,

cathode 26, line 21, back to the condenser 2!].

Tube 22 is biased .by means of a grid circuit ineluding grid 28 in a conventional manner so that when a predetermined charge is placed on 2|] by a predetermined number of impulses, the potential will be great enough to break down the tube 22 and allow the discharge of the condenser 20 through said tube and said circuit. The tube will immediately extinguish itself and condenser measuring them. This means must be accurate and give a direct and linear indication of the time. To accomplish this, a measuring condenser 20 is located in the plate-cathode circuit of tube i5, battery 2| furnishing a source of energy for this circuit. It is obvious that any indicating means capable of reading the number 20 will start charging again from tube l5. The passage of the impulse through winding 24 of transformer 29 will give an impulse in winding30 which will be transmitted to the grid 3! of tube 32. This in turn will cause an impulse to pass through the plate-cathode circuit of said tube,

placing a charge on the second measuring condenser 33, said circuit being from condenser 33, plate 34, cathode 39, battery 2!, line 35, back to condenser 33. In this manner, for each discharge of condenser 20 due to a predetermined number of impulses thereon, an impulse will be placed on condenser 33. For a given frequency, if the time is sufiiciently short, two measuring con- .densers may be enough, and in such cases the number of impulses placed on 33 may be measured and the number of impulses place on 20 may be measured. The question of. accuracy is also involved because the number of digits readable will depend on the number of circuits. In usual practice, it is generally desirable to have a plurality of such circuits so that longer times may be measured or more readable digits provided. It is evident that the more impulses the measuring condenser is made to accumulate before discharging, the more diflicult it will be to determine each increment on a meter because of the decreasing size of the increments on the scale of the meter. The remaining charge on 20 may be measurcd by some means. such as, for example. an inverted electron tube voltmeter having a tube 36 with the plate 31 used as the control electrode. The electronic tube voltmeter circuit. which may be used, will be described in .detail in Fig. 4. As an example of operation, the condenser 20 .may be made to discharge after ten impulses have been placed thereon, so that if the source of constant frequency is kilocycles, condenser 20 will read inmmo second and condenser ,33 will read Home second. It will be evident from the description following that suitable ampliflers may be used if desired bctween winding 30 and grid 3|, and that various means may be used to count the number of impulses in the final stage, such as an electron tube voltmeter or an impulse counter, which will be described in connection with Fig. 4.

One kind of source of constantfrequency and circuit is shown generally in Fig. 2, it being understood of course that this is merely an example and that other circuits and other frequencies may be used. 40 may represent a piezoelectric crystal constant frequency generator of conventional type having an output between terminals M to an amplifier tube 42 with a cathode 43, plate 44 and screen grid 45. An amplified 100 kilocycle source is then present at terminal 46, which may be impressed upon the grid of the first tube. The 100 kc. source shown at 40 may be of different types. The circuit specifically shown is one where a multivibrator, for example, having other frequencies present, is used, and in such a device, the condensers 41 and inductances 48 may be employed to filter out the undesirable frequencies. If the source is a pure frequency, then the filter will not normally be necessary, although it may be used if desired. An example of a switching circuit which can be used is shown in Fig. 3 and is generally similar to that disclosed in application S. N. 408,970. In this circuit, without discussing the details, the impulse at the beginning of the interval is placed across terminals 65. This appears on the control grid 66 of normally non-conducting Thyra/tron tube 51. When this occurs, a current is set up in'the plate circuit of tube S'I from battery 58, resistance 59, galvanometer 60, plate 6|, cathode 62, extinguishing resistance 63, back to the battery 58. When a second, impulse is received at the end of the interval at terminals 6%, normally non-conducting Thyratron" tube 65 becomes conducting, the plate-cathode circuit being established from battery 68, resistance 59, plate 66, cathode 61, back to battery 58. explained in application S. N. 408,970, when tube 66 becomes conducting, the presence of the extinguishing resistance 63 depresses the potential available on plate 6I so that tube 61 is extingu'ished. Battery 10 and resistances II furnish the necessary grid bias for the tubes. It is to be understood, however, that in place of extinguishing resistance, other methods may be used-as disclosed in the prior applications for the de pressing of the plate potential of tube 51. A ballistic galvanometer 60 may be used to give a visual indication of the time of the intervaL-as described in said application's. Such indication, however, will be, momentary only,' as it is a ballistic galvanometer. This galvanometer, if it is employed, could beused to determine the time for counting irregular pulses. The lead 68 from point 69 may then be used to impress the raise of potential on the grid on the first tube of the scaling chronoscope of the present invention so that the source of constant frequency will start to charge the first measuring condenser and continue intermittently to charge the same while the plate circuit of tube 51 is conducting. It is seen, therefore, that conduction will take place in the first tube of-the scaling chronoscope during the positive half cycles of the constant frequency, so that there will be intermittent conduction of tube I during the interval.

Referring now to Fig. 4, there is shown a complete measuring instrument having four count-' ing steps together with a monitoring device and various other circuits, the counting circuits being incascade. It is to be distinctly understood, of course, that more or less counting steps may Then, as

be employed, as desired, such being selected in accordance with the counting ratio between steps, the length of the interval to be measured standard'source of frequency is shown diagrammaticaily at having an output at lead 8| which is connected to the control grid 82 of tube 63. Scaling tube 83 may be of the screen grid type with a screen grid at 94. The standard frequency generator may be similar to that shown in Fig. 2 or any other type desired. The switching circuit shown diagrammatically at 85 may be similar to that shown and described in Fig. 3, although this may also be of any desired type, said switching circuit furnishing asource of potential during the interval to be measured. The control potential of this switching circuit is impressed on grid 62 by lead 86, through a resistance 81. At there is shown diagrammatically a power supply having various terminals which may supply the voltage indicated at each terminal. It is to be understood, of course, that such voltages vary in accordance with the constants of the circuit and tubes used, and are merely illustrative. The switching circuit may obtain its source of negative bias from terminal 9| of the power supply and its positive source through lead 2II, switch 201, lead 2I5, voltage divider 2I6, lead I16 and terminal 94. Terminals 92 may represent the first input terminals of the switching circuit and terminals 93 the second input circuit for the purpose of causing the energization of the switching circuit during the interval. The constant frequency generator may receive its power from terminal 96 through lead 95. 80 of tube 83 may be connected by lead 96, lead 9?, lead 66 to terminal 99 of the power supply. The circuit is so adjusted that when the switching circuit is energized between impulses received at terminals 92 and 93, the grid 82 will be so biased so as to allow conduction in the plate circuit of tube 83 during the positive half cycles of the constant frequency source. 'The plate circuit of tube83 is from terminal IOI of power supply, lead I02, lead I03, lead I04, lead I05, measuring condenser I06, plate I00, cathode 89 to ground. In this way, the condenser I06 will receive a charge during each intermittent conduction of tube 83. Measuring condenser I06 will be charged to a potential with a polarity indicated and the discharge circuit therefore is through lead I05, winding I01 of the transformer I08,

plate I09 of Thyratron" discharge tube IIO,

cathode III, back to the other side of condenser I06." As, explained in connection with Fig. 1, when a predetermined number of impulses have been placed on condenser I06, the breakdown voltage of III! will be reached so that the condenser will discharge through the plate-cathode circuit thereof. The bias on the grid II2 of tube IIO may be. regulated by means of the variable potentiometer II 3, which receives power supply from lead I04, lead I03, lead I02, and terminal IIJI. An impulse through-winding I01 of transformer I08 will cause an impulse to appear on winding I I4,- which will in turn drive the grid I I5 of amplifying tube II6 more negative so as to cause an impulse to appear in the plate-cathode circuit thereof. This plate circuit may be traced from terminal 99, lead 98, lead 91, lead III-resistance II8, plate II9, cathode I20, back to ground at I2I. A condenser I22 may be provided across grid H5 and cathode I20. To improve the shape of the impulses on the grid of tube I I6, 8. conventional condenser I23 is used across the screen grid connection of tube II6. Screen grid I24 of tube IIG may receive its sourceof supply through resistance I25 and lead I03. Due to the negative impulse on the grid II5, the flow through resistance II6 will be decreased so that the potential at point 13 will be raised, thereby placing a positive impulsev on grid I26 of tube I21 through the coupling condenser I28. The grid bias for tube I21 is obtained through resistance I29, lead I30, lead I5'I, point I3I, voltage divider I32, lead I33, to negative terminal III of the power supply. Tube I2'I functions in a manner generally similar to tube 83 so that the impulse placed thereon by the discharge of the preceding measuring condenser I06, causes a fiow in plate- The screen' grid is discharged in this manner when a predeter mined number of impulses have been placed on condenser I34 by the intermittent conduction of tube H0, caused by discharge of condenser I06. The intermittent conduction is amplified by tube H6. The grid I44 of tube I38 is given a proper bias by potentiometer I45, which receives its power supply from lead I46, lead I03, lead I02 and terminal IN. The impulse in winding I40 of transformer I41 is placed upon the grid- I48 of the second amplifying tube I49 in a manner similar to that described for tube H6. A resistance I50 and the condenser II are provided for the purpose of improving the shape of the impulses on tube I49. The transformer I41 is so connected that .the impulse through tube I38 will drive the grid I48 more negative so that the plate current through tube I49 will be decreased. As a result, point I52 will have its potential raised. due, to the decrease in flow through resistance I53, which in turn will raise the potential of grid I54 of tube I55. The grid I54 of tube I55 obtains its bias through the biasing resistance I56, lead I51, point I3I, lead I33 to terminal 9|. A flow is set up'during this pulse through the plate circuit of I55 from terminal IIlI, lead I02, lead i58, the third measuring condenser I59, plate I60, cathode I6I to ground I62. After a predetermined number of pulses have been placed on measuring condenser I59, it .will cause tube I63 to break down and the condenser will be discharged through the plate-cathode circuit thereof through lead I58, winding I64, resistance I65,

plate I66, cathode I61, back to the other side of measuring condenser B59. The bias for the grid I69 of tube I63 will be obtained from variable measuring condenser,

switch I19 may be used to disconnect the counter I1I when desired.

After the interval has been completed, it will be seen that there will be charges present on each of the measuring condensers. The charge on each of these condensers may be measured by means of an inverted electron tube voltmeter which will be described specifically for the first the successive electron tube voltmeters being identical thereto and having the same numerals placed thereon. The charges so measured will be an indication of the number of impulses on each condenser, which in turn will be the number of known time intervals from which the total time interval can be determined. The electron tube voltmeter comprises a. tube I88 and a conventional plate I89, conventional cathode I90, and conventional grid I9I. It is necessary that the leakage in this circuit be a minimum, and for this reason the conventional plate I89 is employed as the control element, and

potentiometer I68. It is to be understood that other counting and amplifying stages may be placed in the circuit, if desired, at this point.

However, if sufficient stages are present to reduce the impulse interval to of a second, an impulse counter may be placed in the circuit responsive to the impulses through transformer I10. Counters are available, such as those manufactured by the Central Scientific Instrument Company, known as the High Speed Cenco Counter, which will indicate directly of a second. Such a counter is indicated diagrammatically at HI, and the impulses therefor may be obtained from winding I12 of transformer I10 through resislance I13 to the grid I14 of amplifier tube I15. As the grid I14 has an impulse placed thereon, the plate-cathode circuit of tube I15 will have a current flow produced therein which will energize the impulse counter I1 I. The

current will flow from terminal 94, lead I16, point I11, lead I18, lead I19, counter I1I, inductance 999, plate I8I, cathode I82, back to ground at I83. The desired impulses on gri'd I14 are positive so that tube L84 is used to eliminate any negative impulses. This is accomplished by connecting tube I84 so that when point 481 becomes n gative with respect to I85, the tube will conduct and short circuit the negative pulse. The

the conventional grid I9I is used as the anode. The tube I88 is in a Wheatstone bridge circuit having apexes I92, I93, I94, I95. The tube is in the leg I92--I95; resistance I96 is in the leg II94; part of resistance I91 is in leg I94-.-I93; and the other part of resistance I91 is in leg I93--I92. It is seen, therefore, that as the potential is changed on control element I89, that the balance will be upset in the bridge and the meter I98 will record the difference or the potential that is present on the measuring condenser I06. The plate I89 is connected to the side of the condenser which becomes negative so that the flow through I88 is reduced as the charge builds up on condenser I06 and therefore the tube cannot be overloaded. I91 is avariable potentiom eter so that the bridge may be suitably balanced. The power supply for the electronic tube voltmeter is across apexes I93 and I95 and is-furnished by battery I99. By this means, each of the electronic tube voltmeters will give an indication of the number of pulses remaining on each of the measuring condensers. Then, if a frequency of kc. and a scaling rate of 10 to 1 in each of the scaling circuits be used, the impulse counter I1I will read .01 second, voltmeter circuit 200 will read .001 second, voltmeter circuit 20I will read .0001 second, and voltmeter circuit 202 will read .00001 second. Other typesof meters or recorders may be used if desired.

In order to reset the device for another operation, it is necessary to discharge the condensers. This may be done by use of the switch shown diagrammatically at 203 having blades 204, 205, 206 and 201 adapted to engage contacts 208, 209, 2) and 2 respectively. A switch operator is shown schematically at 2I2 which may be used for moving the blades in unison. The switch is shown in its resetting position, adapted to discharge the condensers. It is not desirable to discharge thecondensers entirely, but only to the point at which they are completed discharged in operation of the device; and this is approximately 15 volts because the three'discharge tubes are gaseous filled with about a 15 volt terminal drop. It is to be understood, of course, that as the type of tubes or the tube during its life varies, other voltages may be desirable. The three blades are connected together to lead 213, which is connected to the variable potentiometer 2I4, as shown. The contacts 208, 209 and 2I0 are connected to one side of measuring condensers I06, I34 and I59 respectively, and when in closed position will discharge these condensers to the poof both tubes of Fig. 3, and when this is broken,

the tubes are extinguished.

Summarizing the operation of the circuit of Fig. 4', thus far, when the switching circuit 85 receives an impulse at the terminals 92 at the beginning of the interval, the bias of tube 83 will be changed .7 so that the standard frequency source 80 impressed on grid 82 will cause the plate-cathode circuit of 83 to be conducting during the positive pulses of said frequency source. The intermittent conduction of this tube places charges on the first measuring condenser I06. This condenser continues charging until a predetermined number of pulses have been placed thereon, whereupon it is discharged through tube II 0 which places a single charge on the second measuring condenser I34. Measuring condenser I06 continues charging and discharging during the interval. When the second measuring condenser I 34 has received a predetermined number of charges, it wil1 be discharged through tube I38 which will place a single impulse on the next measuring condenser I59, and condenser I34 will continue charging and discharging similar to I06. When measuring condenser I59 has received a predetermined number of charges, it will discharge through tube I63, which will place an impulse on the counter 'I1I. At the end of the interval, a second impulse will be received at terminals 33 of circuit 85, which will extinguish the first tube, and then bias on 82 will again be established such as to render this tube non-conducting. Each of the electron tube voltmeters 202, MI, 200, and the counter I1I will then have a reading thereon which will show the number of pulses which have been received. In order to reset the device, switch 203 is moved to the right (as shown in Fig. 4), discharging the condensers with the input of tube I21 through lead 25I, and

and breaking the switching circuit supply to 85.

It is to be understood, of course, that the particular-type of switch 201 for re-setting the switch circuit 85 depends upon the particular circuit used; also that the number of electron tube voltmeters and measuring condensers may vary in accordance with the use of the instrument. It is also to be pointed out that an irregular number of impulses maybe counted over a definite period by allowing the impulses to be placed upon the grid 82 in place of a standard source of frequency and using a predetermined time interval to operate switching circuit 85. In this manner, the number of impulses received on tube 83 over a given period of time may be counted.

In order to set the instrument and make certain that the sub-multiple ratio or scaling rates are correct, a monitoring device, shown generally at 230', may be used. A conventional cathode ray tube 23I is shown, having vertical defiection plates 232 and horizontal deflection plates 233 with the usual beam focusing plates 234 and grid 235. The negative voltage. for these elements is obtained from the voltage divider 236 and terminal 231 of the power supply. 238 may be the conventional cathode, and condensers 240 the usual by-pass condensers employed in a cathode ray tube circuit. Theswitch shown generally at 24I may have blades 242 and 243 connected together by a schematic switch operator 244. When it is desired to ascertain the scaling rate of the first scaling circuit or the number of pulses placed on measuring condenser I06 for each discharge thereof, switch blades 242 and 243 are placed on contacts 245 and 246 respectively. Tubes 83 and H0 may be considered to be in first scaling circuit, for example. Switch blades 242 will thereby connect the vertical plates 232 through lead 241 with the input frequency of tube 83 or the impulse frequency placed on condenser I06. The switch blade 243 will connect the horizontal plates 233 through lead 248 across measuring condenser I06, which will give the number of discharges of the condenser. The

cathode ray tube will then give an indication of the number of impulses placed on the condenser to a single discharge of the condensentherebygiving the dividing or scaling ratio of this portion of the circuit. Similarly, the scaling rate of the second scaling circuit may be determined by placing switch blades 242 and 243 on contacts 249 and 250, which will connect the vertical plates the horizontal plates across the measuring condenser I34 through lead 252. The second scaling circuit may be considered to include amplifier tube H6 and tubes I21 and I38. In the same manner, the scaling rate of the third circuit may be determined by placing switch blades 242 and 243 on contacts 253 and 254 respectively, which will connect the input of tube I55 through lead 254 to the vertical plates and condenser I53 through lead 255 across the horizontal plates of the cathode ray tube. In this manner, the scaling rateof each circuit may be easily determined and corrected if not that desired. The scaling rate or ratio of impulses received on a measuring condenser to discharge thereof may be adjusted in each of the scaling circuits by altering discharge characteristics of the electronic tube connected across the measuring condenser. This may be accomplished by adjustment of the grid voltage of each of the discharge tubes II 0, I38,

I63, by means of potentiometer II3, I46, I68,

respectively. Other means of changing the scaling rate may be employed, such as varying the screen grid voltage or input signal of the tube employed to charge the measuring condenser. It is evident that the individual scaling rate of each circuit does not necessarily have to be the same, but it is easier to read the same if they are in decimal ratio.

In Fig. 5 will be found diagrammatically an indication of the way in which the device will operate, in which the vertical scale is the voltage across the condenser and the horizontal scale is time. Then the first condenser will be seen to build-up in steps until it reaches the discharge point 256, at which time it will discharge and start building up again to th point 251. At the end of the interval, for example 258, there will predetermined interval, reference being made to the foregoing specification for details of the parts therein. 215 may be the source of irregular impulses,'such as a Geiger-Mueler counter, and 216 the switching circuit similar to 85 of Fig. 4 wherein the impulses placed on 211 and 218 (corresponding to 92 and 93 of Fig. 4) may be indicative of a predetermined time. The scaling circuit is shown in box 219 and may be similar to that just described for Fig. 4 or Fig. 1, the lead 280 corresponding to 19 of Fig. 1. In this use, the device will count the impulses received for a given interval. Where the term recurrent is used in the claims, it may mean regular or irregularly spaced impulses.

The device described herein provides a simple and flexible "counting means for accurately indicating time or impulses for a given time. The invention is to be broadly construed as including all equivalents coming within the scope of the appended claims.

What is claimed is:

1. In a device for'me'asuring intervals, a constant frequency circuit, a normally non-conducting electronic tube having said constant frequency circuit connected thereto; means to rendersaid tube conductive under control of the recurrent pulses of said constant frequency circuit at the beginning of the interval to be measured, a condenser in the plate-cathode circuit of said tube chargeable during each of said conduction pulses by a known increment of charge, a second tube connected to said condenser serving to discharge the condenser after a predetermined number of increments of charge are placed thereon by the recurrent conduction pulses of the first tube, means to render the first tube non-conducting again at the end of the interval, and means to measure the number of discharges of the condenser and the number of increments of charge remaining thereon, thereby directly measuring time.

2. In a device for measuring intervals, an oscillating circuit, a normally non-conducting electronic tube having said oscillating. circuit connected thereto, means to render said tube conductive under control of the recurrent pulses of said oscillating circuit at the beginning of they interval to be measured, a condenser in the platecathode circuit of said tube chargeable during each of said conductions by a known increment of charge, a second tube connected to said condenser serving to discharge the condenser after a predetermined number of increments of charge are placed thereon by the recurrent pulses of the first tube, means to render the first tube non-' conducting again at the end of the interval, and means to measure the number of discharges of the condenser and the number of increments of a charge remaining thereon, thereby giving an indication of the number of impulses during the interval. Y

3. In a device for measuring intervals, an oscillation circuit, a normally biased non-conducting electronic tube having said oscillation circuit connected to a control element thereof, means to bias said tube at the beginning of the interval so that it becomes intermittently conducting during the application thereto of the recurrent pulses of said oscillation circuit during the interval, a condenser in the plate circuit of said tube chargeable with known increments of charge by the recurrent pulses of current in the plate circuit thereof, a second tube connected to said condenser and adapted to become conducting to discharge the condenser after a predetermined number of increments of charge due to recurrent pulses of the first tube have collected on the condenser, means to render the first tube non-conducting at the end of the interval, and means to measure the number of times said second tube becomes conducting during the interval and to measure the number of increments of charge remaining upon the condenser.

4. In an impulse counting device, a source of electrical impulses, a normally non-conducting electronic tube having a control element connected to said source of electrical impulses, variable biasing means connected to a control element to raise the potential of said element during an interval so that -each electrical impulse will render the tube momentarily conducting, a condenser in the plate-cathode circuit of said tube whereby each electrical impulse during the interval places a known increment of charge on said condenser, a second tube connected to said condenser and so biased as to discharge the condenser after a predetermined number of increments of charge have been placed thereon, and means to measure the number of discharges of the. condenser and the number of increments of charge remaining thereon, thereby giving an indication of the number of impulses during the interval.

5. In an impulse counting device, a source of impulses, a normally non-conducting electronic tube having its control element connected to said source of impulses, variable biasing means connected to said control element to raise the potential of said element during an interval so that each impulse will render the tube momentarily conducting, a condenser in the plate-cathode circuit of said tube whereby during the interval each impulse will cause a known increment of charge to appear on the condenser, a second tube connected to said condenser and serving to discharge the condenser therethrough after a predetermined number of increments of charge have appeared thereon, and means to measure the number of times said second tube has discharged the condenser and the increments of charge remaining thereon.

' 6. In an impulse counting device, a source of impulses; a normally non-conducting electronic tube having its control element connected to said source of impulses; biasing means connected to said control element, said bias being variable so that during a predetermined interval each impulse will render the tube momentarily conducting; a condenser in the plate-cathode circuit of said tube whereby each impulse places a known increment of charge on the condenser during the interval; a second tube connected to said condenser and so biased as to discharge the con denser after a predetermined number of increments of charge have been placed thereon; a third tube responsive to the discharge of the condenser through said second tube, said third tube having a condenser in the Plate-cathode circuit thereof which has a known increment of charge placed thereon as a result of each impulse received from the second tube; and means to measure the charges on the measuring condensers, thereby giving an indication of the number of impulses.

7. In a device for measuring intervals, a constant frequency circuit; a normally non-conducting electronic tube having said constant frequency circuit connected thereto; means torenl of charge;

der said tube conductive under control of the recurrent pulses of said constant frequency circuit at the beginning of the interval to be measured; a measuring condenser in the plate-cathode circuit of said tube and chargeable by known increments of charge during said conduction; a plurality of circuits in cascade therewith, each having a measuring condenser and an electronic control tube connected to the preceding measuring condenser, said electronic control tubes discharging the preceding measuring condensers when a predetermined number of increments of stant frequency circuit; a normally non-conducting electronic tube having said constant frequency circuit connected thereto; means to render said tube conductive under control of the recurrent pulses of said constant frequency circuit at the beginning of the interval to be measured; a measuring condenser in the plate-cathode circuit of said tube'and chargeable during each of said conductions by a known increment a plurality of circuits in cascade therewith, each having a measuring condenser and a gaseous tube connected to'the preceding measuring condenser, said measuring condensers being in the plate-cathode circuits of said tubes, each of said gaseous tubes also being connected to discharge the condenser in its plate-cathode circuit and impress a known increment of charge resulting from each discharge on the next measuring condenser; means to render the first tube non-conducting again at the end of the interval;

and means to measure the number of increments of charge on each measuring condenser at the end of the interval.

9. In a device for measuring intervals, a constant frequency circuit; a normally non-conducting electronic tube having said constant frequency circuit connected thereto; means to render said tube conductive under control of the recurrent pulses of said constant frequency circuit at the beginning of the interval to be'measured; a measuring condenser in the plate-cathode circuit of said tube and chargeable by known increments of charge during said conduction; a plurality of circuits in cascade therewith, eachhaving a measuring condenser and an electronic control tube connected thereto, said measuring condensers being in the plate-cathode circuits of said tubes, said electronic control tubes also being connected to discharge the condenser in its plate-cathode circuit and impress a known increment of charge resulting from each discharge on the next -meas uring condenser; means t render the first tube non-conducting again at the end of the interval; and inverted electronic tube voltmeter circuits connected to at least some of the measuring condensers to give a measurement of the number of increments of charge on each.

10. In an electrical counting device, a condenser chargeable in accordance with recurrent impulses; an electronic tube through which said condenser discharges after a predetermined number of impulses have been placed on said condenser thereby giving an impulse for each predetermined number of impulses received on the 75 condenser; a monitoring circuit including a oath"- ode ray tube having two sets of deflection plates, one set being connectable to the condenser to de fiect the beam in accordance with the impulses placed on the condenser and one set of plates being connectable to the electron tube circuitto deflect th beam in accordance with the discharge of thecondenser, thereby giving the counting ra-, 7

tie of the circuit.

11. In an interval measuring device, a condenscr circuit connected to a source of constant frequency during the interval to be measured; an

electronic tube through which said; condenser discharges after a predetermined number of impulses have been placed thereon by the source of constant frequency, said discharges creating impulses which occur with a frequency iwhlch is' asub-m'ultiple of theconstant frequency; and-a monitoring circuit including a cathode my having two sets of beam deflection plates in; ferent planes, one set being conne'ctable to3ibe responsive to the source of"constant frequency,

and the other" set being connectable to b sponsive to a pulse at the discharge of 5 ratio of the constant frequency to the sub-multie ple frequency.

12. In an electrical counting device, an electronic tube responsive to recurrent impulses-during a predetermined interval; a condenser charged with known increments of charge thereby; an electronic control tube having saidcondenser connected in the plate-cathode circuit thereof, said tube being biased so that when a predetermined number of known increments of charge are received on said condenser the condenser will discharge through said electronic control tube; a transformer having one winding in the plate-cathode circuit of said electronic control tube and producing an impulsein the other winding thereof upon dischargeof the condenser; and means to measure the number of increments of charge remaining on the condenser and discharged through said transformer.

13. In a device for measuring intervals, a constant frequency circuit, a normally biased nonconducting electronic tube having said constant frequency circuit connected to a control element thereof, means to bias said tube at the beginning of the interval so that it becomes conductive under control of the recurrent pulses of said constant frequency circuit during the interval, a condenser in the plate circuit of said tube chargeable by known increments of charge by the recurrent pulses, a second tube having said condenser in its plate-cathode circuit and adapted number of increments of charge remaining on the condenser.

14. In an electrical counting device, a source of electrical impulses; a normally biased nonconducting electronic tube; means to change said bias to rendersaid tube conductive under control of the impulses during a predetermined interval; a condenser charged by known increments by each impulse received by said electronic tube during the interval; an electronic control tube have oridenser, thereby giving a visualjndicatiorr' ithe ing a plate-cathode circuit with said condenser therein; means to bias said electronic control tube so that when a predetermined number of known increments of charge are placed on the condenser in the plate circuit of said tube chargeable by known increments of charge due to the recurrent pulses, a second tube having said con-t denser in its plate-cathode circuit and adapted to become conducting to discharge the condenser after a predetermined number of increments of charge due to recurrent pulses of the first tube, a transformer in the plate-cathode circuit of said second tube producing an impulse upon each discharge of the condenser, an amplifier circuit and a measuring condenser connected to said transformer receiving the increments of charge produced by said transformer, means to render the first tube non-conducting at the end of the interval, and means to measure the number of increments of charge on each of the condensers.

COLIN IRVING BRADFORD.

CERTIFICATE or CORRECTION.

Patent No 2, 501,197

It is of the above numbered patent requiring 0nd column, line 5 4,, for line 61+, after The--; page it, second page 5, first column,

column, line 66, line 66, for ratio read ratios-; and that the COLIN IRVING BRADFORD.

"place" read -placed-:-; "measured" insert -and the standard source of frequency.

November 10 142 hereby certified that error appears in the printed specification correction as follows: Page 2, secpage 5, first column,

for "terminal" read -interna1-;

said Letters Patent should be read with this correction therein that the same may conform 'to the record of the case Signed and sealed this 50th day of March,

in the Patent Office,

Henry Van Arsdale,

CERTIFICATE OF CORRECTION.

Patent No. 2,501,197. November 10, 19 2.

COLIN IRVING BRADFORD It is hereby certified thaterror appears in the printed specification iring correction as follows: Page 2, secdpage 5, first column,

of the above numbered patent requ 0nd column, line 514., for piace read -place line 611., after "measured" inser The-' page 14, second column, line 66, for "terminal' read --internal--;

9 page 5, first column, line 66, for""ratio" read --ratios--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 50th day of March, A. '1). 1915.

- Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

t --and the standard source of frequency. 

